The
404 error is one of the standard response codes of the
telnet protocol on which the
web's HTTP is based. The first 4 indicates a client error such as a mistyped
URL. The middle 0 refers to a general syntax error. The last 4
just indicates the specific error in the group of 40x, which in this case is "URL Not Found".
Based on material from FOLDOC, used with permission.